In broadband wireless access communication systems, communication is made between a base station and mobile stations via one direct link, i.e., a wireless communication link with high reliability. However, the fixed location of a mobile station reduces the flexibility in the configuration of a wireless network. This makes it difficult to provide efficient services in a wireless environment where traffic distribution or the amount of call requests varies greatly. In order to resolve this problem, broadband wireless access communication systems employ a relay system that transmits data in a multi-hop form using relay stations near the relay system. In addition, multi-hop relay systems can rapidly re-configure a network in response to a change in an ambient environment, and also manage the entire wireless network more efficiently. Therefore, a self-control adaptive wireless communication network, requested in the next generation mobile communication systems, can be implemented based on a multi-hop relay broadband wireless access communication system.
In a multi-hop relay communication system, a relay station operates in half-duplex mode. The relay station switches a reception mode, where it receives data from a base station, to a transmission mode, and then transmits signals to mobile stations via time slots. When a relay station transmits signals to one mobile station, while a base station is transmitting data to the other mobile stations, the signals transmitted from the base station interfere with the signals transmitted from the relay station to the mobile stations. In that case, the base station experiences limited data transmission.
While the base station transmits data to a relay station via a downlink in the first time slot and then the relay station transmits data to mobile stations in the second time slot, the base station cannot transmit new data to the relay station. Therefore, a conventional data transmission method and system requires twice the amount of time to transmit data from a base station to mobile stations compared to a case where the base station could transmit data without interrupting the data transmission, thereby wasting resources.